Peridontal disease is one of the most widespread medical problems facing the nation today. Crucial to the successful treatment of this disease is early detection as well as careful monitoring of the progress of the periodontal therapy. There are, however, few effective approaches to this problem and for the present, periodontists must still rely very heavily on dental x-rays. Unfortunately, while x-rays provide an excellent way to diagnose dental caries, the quality of x-ray radiographs is not consistantly high enough to obtain reliable data for studying the aveolar bone loss which accompanies periodontal disease. The control of exposure is much more critical in x-rays used for periodontal examination than for those used in basic dentistry because the detection of the boundry of the alveolar bone requires optimum contrast. Radiographic monitoring of chronic destructive peridontal disease is highly dependent on the ability of the clinician to compare sequential radiographs. Although several factors can contribute to the variability of the quality of radiographs, the most important cause is poor control of film exposure. The overall goal of this Phase I-Phase II program is to conduct the detector and instrumentation research needed to make an automatic x-ray exposure controller for use in the diagnosis of periodontal disease. During Phase I, we will focus on the development of the x-ray sensor and demonstrate that it is feasible to use such a device for this purpose. In Phase II of the program, the detector research will be completed and a fully operational experimental, prototype system will be constructed and tested with clinical phantoms in collaboration with the Harvard School of Dental Medicine.